Curator's Take
This research tackles one of the most pressing practical challenges in quantum communications: how to actually build national-scale quantum key distribution networks that can protect critical infrastructure across Europe. Rather than focusing on laboratory demonstrations, the authors provide a concrete methodology for planning real-world QKD deployments, using Austria as a test case to develop scaling rules that could guide infrastructure investments across all EU member states. The work represents a crucial bridge between quantum cryptography research and policy implementation, offering governments the first systematic framework for estimating the scale, cost, and complexity of national quantum communication networks. This type of practical planning research is essential as Europe races to establish quantum-secured communications ahead of the cryptographic vulnerabilities that future quantum computers may create.
— Mark Eatherly
Summary
The European Union is developing the European Quantum Communication Infrastructure (EuroQCI) as a pan-European network to provide secure communication capabilities across Member States, including governmental and critical-infrastructure domains. While the strategic objective is defined at EU level, the required scale and structure of national quantum key distribution (QKD) networks remain largely unspecified. This work addresses the question of how to plan and size national terrestrial QKD networks to support critical infrastructure and public authorities. We propose a reproducible planning methodology that estimates network size, total fiber length, and the number of required QKD components based on a small set of explicit assumptions. The approach is demonstrated for Austria, where a synthetic but structured network model is constructed and evaluated using Monte Carlo simulation. The model focuses on terrestrial QKD infrastructure and explicitly excludes space-based segments. It estimates endpoint counts, trusted repeater node requirements, and hop-length distributions under realistic operational constraints. The Austrian case is then used as a baseline to derive scaling rules for other EU Member States based on population and geographic extent. The results provide first-order planning estimates for national QKD backbone sizes across Europe. These estimates are not intended as deployment designs but as planning-level references that support early-stage cost assessment and infrastructure dimensioning under the EuroQCI framework.